Granted, it isn’t clear how close Kerry was able to get to the glacier, which lies at the end of the World Heritage listed Ilulissat Icefjord, which is often filled with a melange of huge icebergs. On board the HDMS Thetis, a Danish ship, alongside foreign ministers from Greenland and Denmark, Kerry put it like this:

So out of this particular ice fjord, the most active ice flow in the Northern Hemisphere there’s 86 million metric tons of ice each day flowing out into the ice flow, breaking off. I was told coming in here by the pilot of our airplane, who has lived here all his life, that there is enough water being emptied off the ice flow into the Arctic that it would take care of the city — and each day, there is enough water that would take care of the city of New York for an entire year. So this is gigantic transformation taking place and you can see it in the naked eye as you see where the ice has retreated from just in the last 15, 20 years, where the marks are still left.

The figure above, 86 million metric tons of ice per day, may sound impossible to believe. But actually, it translates into 31.39 billion tons per year, which is quite consistent with what one Greenland expert, Ian Joughin of the University of Washington in Seattle, told me about Jakobshavn for an earlier story. He said it’s losing 25 billion to 35 billion tons of ice per year.

And it could actually get worse.

Consider a 2014 study of Jakobshavn by Joughin and three colleagues, which called it “Greenland’s fastest glacier.” Joughin found that its flow speed in 2012 was “nearly three times as great” as in the 1990s. It also found that in just over a decade, between 2000 and 2011, Jakobshavn alone raised sea levels around the globe by almost a millimeter. That may not sound like much, but it means the glacier lost about 360 gigatons, or billion tons, of ice.

As the glacier loses ice in enormous iceberg calving events, it also retreats inland — and, in this case, into a deeper and deeper part of the fjord, where depths are above 1,300 meters. This, in turn, increases the flow speed further.

Thus, the paper predicted that the glacier’s speed could, at the extreme, increase beyond the current factor of three to a factor of 10 faster than in the 1990s, because of its travel through such an incredibly deep basin. In the process, it would retreat backward 50 kilometers (about 30 miles) and hurl forth additional millimeters of global sea level rise.

According to news reports, Kerry was advised on the trip by David Holland, a professor at New York University who studies Greenland and the Antarctic. Holland has previously published research suggesting that Jakobshavn’s great increase in flow speed was triggered by warmer waters reaching its base. Per these reports, Holland said Jakobshavn could actually retreat 100 kilometers (about 60 miles) in the next century.

According to a recent lecture by NASA glaciologist Eric Rignot, Jakobshavn is one of “three major floodgates” for the Greenland ice sheet, which overall contains about 20 feet of potential sea-level rise. Out of this, Jakobshavn contains the potential to contribute almost two feet.

What’s really scary about Jakobshavn, though, is that it’s still nothing like what could happen in parts of Antarctica, where ice volumes are far greater, and glaciers can be even larger. Yet Jakobshavn, because of its size, still gives a hint of what really rapid ice loss could look like there.

Kerry signaled in Greenland that his thinking tends in this direction. Or as he put it:

I wanted to come up here today to both underscore the urgency but also to learn — and I did learn. I learned more about the threat of the Antarctic, which in many ways is far greater than the threat of the ice melt here in Greenland, what I’ve learned today — and an area where we don’t know enough, where we need to do more research, and where we need to respond to greater effect.

No wonder that, floating amid icebergs unleashed by this giant, Kerry spoke bluntly about how just how big the climate-change problem is.

“So what we did in Paris with the Paris accord on global climate change is critical now to be implemented, but it’s not even enough,” he said.